Extras:

Ajax - Asynchronous JavaScript and XML

This technology makes possible web applications which accept user input, communicate with
network servers and resources, and respond to that input, without reloading the web page.

In this demonstration, the user selects a planet from a list. That selection is sent to the
web server where it is processed by a PHP script. The response is sent back to the web browser
which then displays the response without reloading the web page.

In this demonstration, simple static text is returned, but much more complex responses and
interactions are possible. The script on the server could query a database, a distant server,
or facilitate communications between multiple users.